Testing head having vertical probes

ABSTRACT

A testing head having vertical probes is presented. The testing head comprises a guide plate having a guide hole formed therethrough, for accommodating a contact probe having a contact tip that is arranged to mechanically and electrically contact a contact pads on a device under test. The contact probe has a pre-deformed section placed in a flexion region between the guide plate and the test device, arranged to further deform as the contact pad of the test device is drawn against the contacting tip.

BACKGROUND OF THE INVENTION

[0001] 1. Field of The Invention

[0002] The present invention relates to a testing head having verticalprobes, and more particularly to a testing head for use on semiconductorintegrated devices.

[0003] 2. Description Of The Related Art

[0004] As is well known, a testing head is basically a device suitableto electrically interconnect a plurality of contact pads of amicrostructure and the corresponding channels of a testing machinearranged to perform the tests.

[0005] Integrated circuits are factory tested in order to spot andreject any circuits that show out to be already defective during themanufacturing phase. The testing heads are normally employed toelectrically test the integrated circuits “on wafer”, prior to cuttingand mounting them in a chip package.

[0006] A vertical probes testing head comprises at least a pair ofparallel guide plates placed at a given distance apart to leave an airgap therebetween, and a plurality of specially provided movable contactelements. In particular, the guide plate pair comprises a top guideplate and a bottom guide plate, both plates being formed with guideholes receiving the movable contact elements for axial sliding movementtherethrough, the contact elements being usually wires made of specialalloys having good electrical and mechanical properties. These will bereferred to as the testing head probes through the remainder of thisdescription.

[0007] A good contact of the testing head probes with the contact padsof a device to be tested is achieved by urging the testing head againstthe device, with the movable contact probes flexed in the air gapbetween the two guide plates. Testing heads of this type are commonlyknown as “vertical probes”.

[0008] In other words, conventional testing heads have an air gap wherethe probes are flexed, with such flexion being assisted by a suitableconfiguration of the probes or their guide plates, as schematicallyshown in FIG. 1.

[0009] As shown in FIG. 1, a testing head 1 comprises at least a topguide plate 2 and a bottom guide plate 3, both formed with top 4 andbottom 5 guide holes, respectively, through which at least one contactprobe 6 slides.

[0010] Each contact probe 6 has at least one contact end or tip 7. Inparticular, the contact tip 7 is caused to abut against a contact pad 8of a device to be tested, thereby establishing a mechanical andelectrical contact between said device and a testing apparatus (notshown) that has said testing head as end element.

[0011] The top and bottom guide plates 2 and 3 are suitably separated byan air space or gap 9 accommodating the deformation of the contact probe6. Moreover, the top and bottom guide holes 4 and 5 are suitable sizedto guide the contact probe 6.

[0012] The deformed pattern of the probes, and the force required toproduce it, depend on a number of factors, such as:

[0013] the physical characteristics of the alloy used in theconstruction of the probes; and

[0014] the amount of offset between the guide holes in the top guideplate and the corresponding guide holes in the bottom guide plate, aswell as the distance between such holes.

[0015] It should be noted that, for a correct testing head operation,the probes must have a suitable degree of free axial movement in theguide holes. In this way, the probes can also be taken out and replacedin the event of a single probe breaking, with no need to replace thewhole testing head.

[0016] All these features are, therefore, to be taken into due accountin the manufacture of a testing head, given that a good electricconnection between the probes and the device to be tested is mandatory.

[0017] Also known is to use contact probes having a pre-deformedconfiguration even when the testing head 1 is not contacting the deviceto be tested, as in the probes 6 b and 6 c shown in FIG. 1. Thispre-deformation effectively helps the probe to correctly flex during itsoperation, i.e. upon contacting the device to be tested.

[0018] Thus, the correct operation of a testing head depends on thevertical movement, or overtravel, of its probes, and the horizontalmovement, or scrub, of the probe contact tips.

[0019] In conventional testing heads, these parameters have inherentlimitations. As schematically shown in FIGS. 2A and 2B, the maximumovertravel of a probe is equal to the length of the probe portion Aprojecting out with respect to the bottom guide plate, this projectingportion A being retracted into the bottom guide plate as the testinghead contacts the device to be tested, by virtue of the probe flexionand deformation.

[0020] However, the height of such projecting portion is limited by theprobe fragility properties, and is usually 300 to 500 μ.

[0021] In practice, the above overtravel amount of the probes is onlytheoretically achievable, and problems due to probes becoming stuck intheir guide holes and due to the permanent deformation of the probesalready arise for very small overtravel amounts.

[0022] This problem has been circumvented by using probes with adeformation in their section lying within the air gap, as schematicallyshown in FIG. 2C. Such probes utilize almost all the overtravel of theprojecting portion from the bottom guide plate, but are complicated tomanufacture and maintain.

[0023] In addition, the bottom guide plate greatly restricts thehorizontal movements of the probe tip, the extent of this movement orscrub being strictly dependent on the difference between the diametersof the hole and the probe.

[0024] In some cases, the contact probes are fixedly mounted to the topguide plate of the testing head. This arrangement is known as a testinghead having clamped contact probes.

[0025] However, testing heads with loose-mounted probes are more widelyemployed, wherein the probes are interfaced to a “board” by amicrocontact strip called the “space transformer”. This is known as atesting head having no-clamped contact probes.

[0026] In the latter case, each contact probe has an additional contacttip pointing toward a plurality of contact pads provided on the spacetransformer. A good electric contact is established between the probesand the space transformer in a similar way as the contact to the deviceto be tested, i.e. by urging the probes against the contact pads on thespace transformer.

[0027] The major advantage of a testing head having no-clamped contactprobes is that one or more faulty probes, or the whole set of probes,can be replaced with greater ease than is allowed by testing headshaving clamped contact probes.

[0028] In this case, however, the top and bottom guide plates must bedesigned to withhold the contact probes in place even while no device tobe tested is abutting their contact tips, or when the whole set ofprobes is removed for replacement.

SUMMARY OF THE INVENTION

[0029] Embodiments of this invention provide testing heads formicrostructures, which have probes adapted to be deformed on touchingcontact pads to establish a good electric contact to a device to betested, and adapted to be held in place without the assistance of abottom guide plate.

[0030] One of the principles on which embodiments of the presentinvention stand is one of providing a testing head with a plurality ofprobes, each having a pre-deformed section between the testing head andthe device to be tested.

[0031] Presented is a testing head comprising a guide plate having aguide hole formed therethrough and adapted to receive a contact probehaving a contacting tip arranged to mechanically and electricallycontact a contact pad of a test device, said contact probe having apre-deformed section placed in a flexion region between the guide plateand the test device, said pre-deformed section being arranged to furtherdeform as the contact pad of the test device is drawn against thecontacting tip. Additionally presented is a method of creating anelectro/mechanical connection between a testing head and a test device.

[0032] The features and advantages of a testing head according to theinvention will be apparent from the following description of embodimentsthereof, given by way of nonlimiting examples with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a cross-sectional view of a testing head according to anembodiment of the prior art;

[0034]FIGS. 2A, 2B and 2C are cross-sectional views of a testing headaccording to further embodiments of the prior art;

[0035]FIG. 3 is a cross-sectional view of a testing head according to anembodiment of the invention;

[0036]FIGS. 4A, 4B, 4C, 4D and 4E are cross-sectional views of a testinghead according to further embodiments of the invention;

[0037]FIGS. 5A and 5B are cross-sectional views of a testing headaccording to another embodiment of the invention;

[0038]FIGS. 5C and 5D are top plan views of alternative arrangements ofa testing head according to an embodiment of the invention;

[0039]FIGS. 6A and 6B is a cross-sectional view of a testing headaccording to further embodiments of the invention;

[0040]FIGS. 7A, 7B, 7C and 7D are cross-sectional views of a testinghead according to further embodiments of the invention; and

[0041]FIGS. 8A. 8B and 8C are cross-sectional views of a testing headaccording to further embodiments of the invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] With reference to FIG. 3, a testing head 10 according to anembodiment of the invention, suitable to be placed in contact with adevice 11 to be tested or test device, is shown.

[0043] The testing head 10 comprises at least one guide plate 12 formedwith at least one guide hole 13 for receiving a contact probe 14.

[0044] The contact probe 14 has a symmetrical or asymmetricalpre-deformed section 15, placed in a flexion region 19 extending betweenthe guide plate 12 and the device 11 to be tested. This pre-deformedsection can also deform during normal operation of the testing head 10.In particular, the contact probe 14 has a contact end or tip 16 intendedto abut against corresponding contact pads 17 of the device 11 to betested and to cause a further deformation of the probe 14 at itspre-deformed section 15.

[0045] The testing head 10 shown in FIG. 3 has no-clamped contactprobes, each probe having an additional contact tip 18 pointing toward aspace transformer 20. This is given by way of non-limiting example of atesting head according to an embodiment of the invention. Alternatively,it would be plainly possible to provide a testing head 10 havingpre-deformed clamped probes.

[0046] Advantageously according to embodiments of the invention, theflexion region 19 lies outside the testing head 10, between the guideplate 12 and the device 11 to be tested. In this way, the problems thatbeset conventional testing heads, due to probes becoming stuck in theirguide holes, or due to the size of the air gap between the guide platesand, hence, the testing head space requirements, are overcome.

[0047] Furthermore, since the flexion region 19 is placed outside thetesting head 10, the amount of possible vertical movement or overtravelfor the testing head 10 can be increased.

[0048] Moreover, the horizontal movement or scrub of the contact tip 16on the contact pads 17 is easily controlled by suitably changing thesize and shape of the pre-deformed section 15 of the probe 14.

[0049] Shown in FIGS. 4A, 4B, 4C, 4D and 4E are representativeembodiments of the testing head 10 according to the invention,specifically providing a range of different shapes for the pre-deformedsection 15 of the probe 14.

[0050] In particular, the probe shown in the embodiment of FIG. 4A hasits pre-deformed section 15 symmetrical and essentially oval in shape.The contact tip of this probe makes no horizontal movement (scrub), andthe probe vertical movement (overtravel) is taken up by a deformationoccurring in its pre-deformed section 15, which is in any casesymmetrical.

[0051] With this configuration, a horizontal movement (scrub) having apreset amount and direction can be obtained by using a pre-deformedsection 15 having one leg with a different cross-section from the otheror mirror-image leg.

[0052] The probes shown in the embodiments of FIGS. 4B, 4C and 4E haveeach a pre-deformed section 15 of asymmetrical shape, and first andsecond slanted (e.g. vertical) extensions 15 a and 15 b that aresuitably offset from each other to cause the horizontal movement (scrub)to occur along a given direction. It is also possible to use a probe 14having a C-shaped pre-deformed section 15, such section having the first15A and second 15B extensions suitably slanted (e.g. vertical), so thata horizontal movement (scrub) occurs, which depends on the contactgeometry, as shown in FIG. 4D.

[0053] Advantageously according to embodiments of the invention, theprobes 14 may be formed with a non-circular cross-sectional shape. In apreferred embodiment, schematically shown in FIGS. 5A and 5B, a probe 14with a rectangular cross-sectional shape is provided. In this case, itscorresponding guide hole 13 in the plate 12 should also have arectangular cross-sectional shape, the probes 14 passing through suchholes being always aligned to the contact pads 17 of the device 11 to betested.

[0054] Using a rectangular cross-sectional probe as shown in FIG. 5A,the deformed of the probe 14 in the plane of the pre-deformed section 15is better controlled when the probe contacts the device 11 to be tested,the movement occurring in a predetermined plane such that differentrectangular cross-sectional probes will retain the same orientationduring their vertical or overtravel movement.

[0055] Major advantages of a probe 14 formed with a non-circularcross-section are:

[0056] a better orientation of the probes at the testing head assemblingphase by reason of the match provided between the guide holes and theprobes;

[0057] a better controlled deformation during the contact of the probetip to the pads of a device to be tested; and

[0058] easier replacement of faulty probes in a self-centered position,once the relative positions of the guide holes and the contact pads areset, and accordingly, more convenient servicing of the testing head.

[0059] Advantageously according to further embodiments of the invention,a testing head 10 carries a plurality of probes 14 formed with apre-deformed section 15 and orientated according to a symmetricalpattern of their deformed sections relative to a row of contact pads, asshown in FIG. 5C, or according to a mirror-image pattern relative to twoadjacent rows of contact pads, as shown in FIG. 5D, minimizing the bulkdimensions of the plurality of probes and, therefore, of the testinghead.

[0060] In a preferred embodiment, wherein the testing head 10 has probes14 orientated according to a symmetrical pattern, for example, suchprobes 14 have non-circular cross-section for more convenientorientation of the deformed sections, each probe 14 being rotatedthrough a suitable angle, e.g. 180°, one from the other. In particular,the cross-sectional shape is a rectangle with the small side in the sameplane as the deformed section, as shown in FIG. 5A, to have the probe 14oriented in the right direction, even when the probe is deformed.

[0061] In a further embodiment of the invention, as schematically shownin FIGS. 6A and 6B, an area 21 of frictional engagement of the probe 14in its guide hole 13 through the guide plate 12 is provided to preventthe probe 14 from dropping off the guide hole 13 while no device 11 tobe tested is positioned.

[0062] This further embodiment is specially suitable for use with aspace transformer 20, wherein the probe 14 is held in the guide 12 onlyby frictional engagement.

[0063] According to a preferred embodiment, the probe 14 is providedwith an additional pre-deformed section 22 extending inside the guidehole 13, as shown in FIG. 6A, to form the area 21 of frictionalengagement of the probe 14 in the guide hole 13.

[0064] A target amount of frictional engagement is obtained by suitablyselecting the shape of this additional pre-deformed section 22 and thedimensions of its guide hole 13.

[0065] Alternatively, the area 21 of frictional engagement could beprovided by using guide holes 13 slanting from a perpendicular line tothe plane containing the device 11 to be tested, i.e. from the verticallay of the probes 14, as schematically shown in FIG. 6B. In the samemanner, curvilinear guide holes 13 could be also considered.

[0066] According to a further embodiment of the invention, slanting orcurvilinear guide holes are used for probes 14 incorporating saidadditional pre-deformed section 22, so as to increase the frictionalengagement generated in said area 21 of frictional engagement of theprobe 14 in the guide hole 13.

[0067] According to an alternative embodiment, the guide plate 12comprises a top guide hole having an S-like pattern; or differentpatterns, e.g. a curvilinear pattern, for increasing the frictionalengagement of the probes in the guide holes.

[0068] It should be noted that, although a single guide plate 12accommodating the probes 14 has been described thus far, several suchguide plates could be used instead.

[0069] According to further embodiments of the invention, the testinghead 10 comprises two or more juxtaposed guide plates 12 a, 12 b, . . ., 12 n, which are suitably offset from one another to create a combinedarea 21 a of frictional engagement between the probes 14 and the guideplates 12 a, 12 b, . . . , 12 n, as schematically shown in FIGS. 7A and7B.

[0070] The guide plates 12 a, 12 b, . . . , 12 n are in mutual contactrelationship, and can be assembled such that each guide hole and eacharea 21 of frictional engagement have non-straight patterns, accordingto more or less complicated forms, to increase the probe 14 retainingforce in the guide plates.

[0071] According to another embodiment of the invention the guide plate12 is overlaid by an elastic film 23 to increase the probe 14 retainingforce inside the guide hole 13, as schematically shown in FIG. 7C.

[0072] This elastic film 23 would increase the probe-to-hole frictionforce, and with it, the probe retaining force in the guide plate.

[0073] Finally, according to a further embodiment of the invention, twoor more juxtaposed guide plates 12 a, 12 b, . . . , 12 n, not offsetfrom each other, are used to receive at least one probe 14 provided withan additional pre-deformed section 22 for retaining the probe within theguide holes 13, as schematically shown in FIG. 7D.

[0074] It should be emphasized that the embodiments of the testing head10 described hereinabove increase the probes 14 retaining force withinthe guide holes 13 without interfering with any of the operations forreplacing faulty probes 14, the operations of pulling out and pulling inthe probes 14 being here much simpler to perform than in conventionaldesigns, due to the pre-deformed section 15 having been located outsidethe testing head 10.

[0075] To summarize, the testing head 10, according to a preferredembodiment of the invention, comprises at least one probe 14 having apre-deformed section 15 located in a flexion region 19 outside thetesting head 10, on the same side as a device 11 to be tested. Theflexion of this pre-deformed section takes up the probe 14 verticalmovement or overtravel upon the probe tip 16 contacting a pad 17 of thedevice 11 to be tested, whether or not the probe overtravel isaccompanied by a horizontal movement or scrub of the contact tip 16depending on the shape of the pre-deformed section 15.

[0076] Broadly speaking, pre-deformed sections 15 with differentdimensions and symmetrical or asymmetrical shapes may be provided, ofwhich some non-limiting examples are shown in FIGS. 8A, 8B and 8C. It isunderstood, however, that these examples are not exhaustive of allpossible shapes for the pre-deformed sections 15 of the probes 14 of atesting head 10 according to the invention.

[0077] Changes can be made to the invention in light of the abovedetailed description. In general, in the following claims, the termsused should not be construed to limit the invention to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all methods and devices that are in accordance withthe claims. Accordingly, the invention is not limited by the disclosure,but instead its scope is to be determined by the following claims.

1. Testing head having vertical probes and comprising: a guide platehaving a guide hole formed there through; and a contact probe adapted tobe received in said guide hole and having a contacting tip arranged tomechanically and electrically contact a contact pad of a test device,wherein said contact probe has a pre-deformed section placed in aflexion region between the guide plate and the test device, saidpre-deformed section being arranged to further deform as the contact padof the test device is drawn against the contacting tip.
 2. The testinghead of claim 1, further comprising a plurality of probes havingpre-deformed sections symmetrically orientated with a row of contactpads.
 3. The testing head of claim 1, further comprising a plurality ofprobes having pre-deformed sections orientated in mirror-imagerelationship with two rows of contact pads.
 4. The testing head of claim1, further comprising a plurality of probes having pre-deformed sectionsorientated in mirror-image relationship with two adjacent rows ofcontact pads.
 5. The testing head of claim 1, wherein an area offrictional engagement is provided between said probe and said guide holeto prevent the probe from dropping off the guide hole when no device tobe tested is positioned.
 6. The testing head of claim 5, wherein saidprobe comprises an additional pre-deformed section lying inside saidguide hole to enhance the frictional engagement in said area.
 7. Thetesting head of claim 5, wherein said guide hole is slanted from aperpendicular line to the plane containing the test device, and producessaid area of frictional engagement.
 8. The testing head of claim 5,wherein said guide hole is curvilinear from the perpendicular line tothe plane containing the test device and produces said area offrictional engagement.
 9. The testing head of claim 5, wherein saidprobe comprises an additional pre-deformed section provided within saidguide hole, and said guide hole is slanted from a perpendicular line tothe plane containing the test device and produces said area offrictional engagement.
 10. The testing head of claim 5, wherein saidprobe comprises an additional pre-deformed section provided within saidguide hole, and said guide hole is curvilinear and produces said area offrictional engagement.
 11. The testing head of claim 1, wherein saidpre-deformed section is symmetrical in shape.
 12. The testing head ofclaim 1, wherein said pre-deformed section is asymmetrical in shape. 13.The testing head of claim 11, wherein said pre-deformed section isessentially oval and symmetrical in shape.
 14. The testing head of claim12, wherein said pre-deformed section is C-shaped with suitably slantedfirst and second extensions that are aligned to each other.
 15. Thetesting head of claim 12, wherein said pre-deformed section is C-shapedwith first and second vertical extensions that are aligned to eachother.
 16. The testing head of claim 12, wherein said pre-deformedsection is C-shaped with first and second extensions that are suitablyslanted and offset from each other.
 17. The testing head of claim 12,wherein said pre-deformed section is C-shaped with first and secondvertical extensions that are suitably offset from each other.
 18. Thetesting head of claim 1, further comprising two or more guide platesarranged in mutual contact relationship to provide said guide hole. 19.The testing head of claim 18, wherein said guide plates are mutuallyoffset and provide for a guide hole with a non-straight section.
 20. Thetesting head of claim 1, wherein an elastic film overlies said guideplate and enhances the retaining force of said probe in said guide hole.21. The testing head of claim 1, wherein said probe has a non-circularcross-sectional section.
 22. The testing head of claim 1, wherein saidprobe has a rectangular cross-sectional shape.
 23. The testing head ofclaim 1, wherein said probe has a rectangular cross-sectional shape withthe small side of the rectangle lying on the same plane as saidpre-deformed section.
 24. A testing head having vertical probes andcomprising: a guide plate having a guide hole formed there through; anda contact probe adapted to be received in said guide hole and having acontacting tip arranged to mechanically and electrically contact acontact pad of a test device, wherein, as a contact pad of a test deviceis placed against the contacting tip of the contact probe, said contactprobe is structured to deform in a flexion region between the guideplate and the test device.
 25. The testing head of claim 24, whereinsaid contact probe has a pre-deformed section placed in said flexionregion, said pre-deformed section being arranged to further deform asthe contact pad of the test device is drawn against the contacting tip.26. The testing head of claim 24, further comprising a plurality ofprobes having pre-deformed sections symmetrically orientated with a rowof contact pads.
 27. The testing head of claim 24, further comprising aplurality of probes having pre-deformed sections orientated inmirror-image relationship with two rows of contact pads.
 28. The testinghead of claim 24, further comprising a plurality of probes havingpre-deformed sections orientated in mirror-image relationship with twoadjacent rows of contact pads.
 29. The testing head of claim 24, whereinan area of frictional engagement is provided between said probe and saidguide hole to prevent the probe from dropping off the guide hole when nodevice to be tested is positioned.
 30. The testing head of claim 29,wherein said probe comprises an additional pre-deformed section lyinginside said guide hole to enhance the frictional engagement in saidarea.
 31. The testing head of claim 29, wherein said guide hole isslanted from a perpendicular line to the plane containing the testdevice, and produces said area of frictional engagement.
 32. The testinghead of claim 29, wherein said guide hole is curvilinear from theperpendicular line to the plane containing the test device and producessaid area of frictional engagement.
 33. The testing head of claim 29,wherein said probe comprises an additional pre-deformed section providedwithin said guide hole, and said guide hole is slanted from aperpendicular line to the plane containing the test device and producessaid area of frictional engagement.
 34. The testing head of claim 29,wherein said probe comprises an additional pre-deformed section providedwithin said guide hole, and said guide hole is curvilinear and producessaid area of frictional engagement.
 35. The testing head of claim 24,wherein said pre-deformed section is symmetrical in shape.
 36. Thetesting head of claim 24, wherein said pre-deformed section isasymmetrical in shape.
 37. The testing head of claim 35, wherein saidpre-deformed section is essentially oval and symmetrical in shape. 38.The testing head of claim 36, wherein said pre-deformed section isC-shaped with suitably slanted first and second extensions that arealigned to each other.
 39. The testing head of claim 36, wherein saidpre-deformed section is C-shaped with first and second verticalextensions that are aligned to each other.
 40. The testing head of claim36, wherein said pre-deformed section is C-shaped with first and secondextensions that are suitably slanted and offset from each other.
 41. Thetesting head of claim 36, wherein said pre-deformed section is C-shapedwith first and second vertical extensions that are suitably offset fromeach other.
 42. The testing head of claim 24, further comprising two ormore guide plates arranged in mutual contact relationship to providesaid guide hole.
 43. The testing head of claim 42, wherein said guideplates are mutually offset and provide for a guide hole with anon-straight section.
 44. The testing head of claim 24, wherein anelastic film overlies said guide plate and enhances the retaining forceof said probe in said guide hole.
 45. The testing head of claim 24,wherein said probe has a non-circular cross-sectional section.
 46. Thetesting head of claim 24, wherein said probe has a rectangularcross-sectional shape.
 47. The testing head of claim 24, wherein saidprobe has a rectangular cross-sectional shape with the small side of therectangle lying on the same plane as said pre-deformed section.
 48. Amethod for creating an electro/mechanical connection between a testinghead and a test device, the method comprising: holding a contacting tipof a contact probe in the testing head in correspondence to a contactpad on the test device; causing the contacting tip of the contact probeto abut against the contact pad as the device to be tested is pressedagainst the contacting tip; providing a pre-deformed section of thecontact probe in a flexion region between the guide plate and the testdevice; and causing the contact probe to deform in correspondence ofsaid pre-deformed section, as the device to be tested is further pressedagainst the contacting tip.
 49. The method of claim 48, wherein holdinga contacting tip of a contact probe in the testing head comprisesholding a portion of the contact probe in a frictional relationship withthe guide hole.
 50. The method of claim 49, wherein said probe comprisesan additional pre-deformed section lying inside said guide hole.
 51. Themethod of claim 49, wherein said guide hole is slanted from aperpendicular line to the plane containing the test device.
 52. Themethod of claim 49, wherein said guide hole is curvilinear.
 53. Themethod of claim 49, wherein said probe comprises an additionalpre-deformed section provided within said guide hole, and that saidguide hole is slant from a perpendicular line to the plane containingthe test device.
 54. The method of claim 49, wherein said probecomprises an additional pre-deformed section provided within said guidehole, and that said guide hole is curvilinear.
 55. The method of claim48, further comprising, before the contact pad touches the contactingtip: inserting a plurality of contact probes having pre-deformedsections through a plurality of guide holes wherein said pre-deformedsections of the contact probes are symmetrically orientated with a rowof contact pads.
 56. The method of claim 48, further comprising, beforethe contact pad touches the contacting tip: inserting a plurality ofcontact probes having pre-deformed sections through a plurality of guideholes wherein said pre-deformed sections of the contact probes areorientated in mirror-image relationship with two rows of contact pads.57. The method of claim 48, further comprising, before the contact padtouches the contacting tip: inserting a plurality of contact probeshaving pre-deformed sections through a plurality of guide holes whereinsaid pre-deformed sections of the contact probes are orientated inmirror-image relationship with two adjacent rows of contact pads. 58.The method of claim 48, wherein providing a pre-deformed section of thecontact probe comprises providing a pre-deformed section symmetrical inshape.
 59. The method of claim 48, wherein providing a pre-deformedsection of the contact probe comprises providing a pre-deformed sectionasymmetrical in shape.
 60. The method of claim 58, wherein saidpre-deformed section is essentially oval and symmetrical in shape. 61.The method of claim 59, wherein said pre-deformed section is C-shapedwith suitably slanted first and second extensions that are aligned toeach other.
 62. The method of claim 59, wherein said pre-deformedsection is C-shaped with first and second vertical extensions that arealigned to each other.
 63. The method of claim 59, wherein saidpre-deformed section is C-shaped with first and second extensions thatare suitably slanted and offset from each other.
 64. The method of claim59, wherein said pre-deformed section is C-shaped with first and secondvertical extensions that are suitably offset from each other.
 65. Themethod of claim 48, wherein holding a contacting tip of a contact probein the testing head comprises providing two or more guide platesarranged in mutual contact relationship to form said guide hole.
 66. Themethod of claim 65, wherein said guide plates are mutually offset andprovide for a guide hole with a non-straight section.
 67. The method ofclaim 48, further comprising applying a layer of elastic material tosaid guide plate.
 68. The method of claim 48, wherein said probe has anon-circular cross-sectional section.
 69. The method of claim 48,wherein said probe has a rectangular cross-sectional shape.
 70. Themethod of claim 48, wherein said probe has a rectangular cross-sectionalshape with the small side of the rectangle lying on the same plane assaid pre-deformed section.